The present invention relates to sliding guides used in elevator systems. More particularly, the invention relates to a sliding guide vibration isolator.
Elevator cars are commonly guided along rails in a hoistway by sliding guides. In elevator systems including sliding guides, it has been a frequent practice to interpose an elastomeric material between the car and the guide which slides against the rail. This is done in an attempt to reduce the transmission of mechanical vibration and acoustical noise into the car and its passengers.
Prior sliding guides including elastomeric vibration isolating arrangements have several disadvantages. The stiffness of such sliding guides is too high for effective vibration and acoustic noise reduction, despite the use of elastomeric material between the car and rail sides of the device. The weight of the car and its associated load has a center of gravity whose location varies depending on the number of passengers and their locations within the car. This creates significant side-to-side forces which the sliding guides must transmit to the rails. In addition, the horizontal distance between the rails varies slightly along the height of the hoistway due to installation tolerances. Such rail imperfections also affect the forces applied to the sliding guides. These forces vary and so cannot be accommodated by a low stiffness isolator, which could provide useful amounts of vibration and acoustic noise reduction. This situation necessitates a higher stiffness mounting design, which affords little sound and vibration reduction in the lower frequency range. Unfortunately, the lower frequency range contains significant vibration and acoustic noise energy which is objectionable in the car.
In prior sliding guides, the elastomeric material is constrained over most of its surface by either the sliding guide or the supporting bracket which is attached to the car. Only a small fraction of the elastomer's surface area is exposed to the air where it would be free to “bulge out” under the action of forces applied to the guide. As the elastomers frequently used are incompressible, the only way for the guide to move relative to the supporting bracket is for the entire volume of elastomer to “flow” towards the exposed edges to “bulge out”. As a consequence of a small area through which the elastomer is free to bulge, the stiffness of this arrangement is often much higher than the stiffness needed for the significant reduction of vibration and acoustic noise. Instead of a highly constrained elastomer, some prior sliding guides use a resilient element, such as a mechanical spring. In either case, these materials provide little or no dynamic mechanical isolation and damping, resulting in poor vibration and acoustic noise reduction in some frequency ranges due to the interaction of lightly damped (and thus high amplitude) mechanical resonances in the car, rail, sliding guide and elevator system structures and materials.
In light of the foregoing, the present invention aims to resolve one or more of the aforementioned issues that afflict elevator systems.